1. Field of the Invention
The present invention relates to an organic EL (electroluminescence) element and to a process for manufacture of the organic EL element.
2. Related Background Art
The announcement by Kodak Corp. of a laminated organic EL element having an organic layer formed by vacuum vapor deposition using a low molecular compound eventually led to energetic development of organic EL displays, many of which are currently being implemented.
At the same time, further improvements are being researched for the characteristics of organic EL elements. Conventional organic EL elements are generally known which employ materials with electron transport capacity, such as aluminoquinolinol complexes, in the luminescent layers, electron transfer layers and electron injection layers. However, despite the high luminescent brightness of such organic EL elements, the luminescent efficiency has not been satisfactory in all cases. Insufficient luminescent efficiency requires an increased driving voltage for light emission, thus resulting in a reduced usable life of the organic EL element.
In order to provide organic EL elements which uniformly emit light at high efficiency, there have been proposed organic EL elements having an insulating metal oxide with an energy gap of 4.0 eV or greater inserted between the luminescent layer and negative electrode, for instance (for example, see Japanese Unexamined Patent Publication HEX No. 5-3080). For improved high efficiency and usable life, there have been proposed organic EL elements provided with an insulating layer between the luminescent layer and the positive and negative electrodes (for example, see U.S. Pat. No. 5,853,905).